Several Crystal Growth And Properties Of Scheelite Structure

In the past decades there are a great deal of interest and development in tungstate crystal in the fields such as electron paramagnetic resonance, dielectric properties, microstructure, laser properties, Raman spectra characteristics and stimulated Raman scattering. Tungstate crystals have good physical and laser properties. In addition, tungstate crystals have greater stimulated Raman scattering properties due to the [WO₄]^2- with higher x³ coefficient than other crystals. At the same time, as a doped ion, Yb³⁺ has more advantages than Nd³⁺ that was prevalently used in the previous. In the early 1990s, with the development and cost deflation of the InGaAs LD (0.87-1.1μm), much attention has been paid to the Yb³⁺ doped laser crystal.Although tungstate crystals have good physical and laser properties, there are not a lot of researches for Yb³⁺ doped tungstate crystal with the scheelite structure according to our knowledge. The tungstate crystals with little dimensions and low optical quality are the key to limit the laser properties study of tungstate crystal. In this dissertation, the growth, structure, defects and physical properties of Yb³⁺ doped NaGd(WO₄)₂, NaY(WO₄)₂, SrWO₄ crystals as well as their laser properties are systemically studied. In addition, the applications of SrWO₄ crystal in Roman lasers are also discussed. The outline of this dissertation is as follows:1. Crystal GrowthAccording to the phase diagram of these tungstate crystals, we can know they are congruent melting composition and there are not the phase transitions under their melt temperature. Therefore, Yb³⁺ doped NaGd(WO₄)₂, NaY(WO₄)₂, SrWO₄ crystals with high optical quality and large dimensions were successfully grown along a- direction by the Czochralski method. The factors that affect quality of crystals during the growth were analyzed and the measures to resolve the characteristics of these factors were presented.2. Crystal Components, Structure and DefectsThe XRPD patterns of crystal polycrystalline materials, the as-grown crystals, the...